Windows: generate-pcm errors when running GitHub action

[cachemeifyoucan]

Currently, the only issue in GitHub action is windows failing with generate-pcm errors on windows.

Error message:

2025-12-04T20:49:20.3805316Z <EXPR>:0: error: ExplicitModuleBuildTests.testEmitModuleSeparatelyJobs : threw error "errors were encountered"
2025-12-04T20:49:20.3805738Z 
2025-12-04T20:49:20.3806031Z Test Case 'ExplicitModuleBuildTests.testEmitModuleSeparatelyJobs' failed (0.37 seconds)

...
2025-12-04T20:49:20.4579733Z error: generate-pcm command failed with exit code 1 (use -v to see invocation)

This is failing multiple tests. After fixing this, we need to see how we can make sure swift-driver tests are not broken by swift compiler changes.

[compnerd]

Tested locally, this has already been fixed by @hjyamauchi and is in the swift frontend. The VFS was not being passed to the frontend when emitting the PCM resulting in the failures. I've tested this locally with the 12/1 snapshot and it does fix it.

[hjyamauchi]

This was the fix swiftlang/swift#85325

[cachemeifyoucan]

I think the windows images are not up-to-date maybe? https://hub.docker.com/layers/swiftlang/swift/nightly-windowsservercore-ltsc2022/

[cachemeifyoucan]

@compnerd Is it possible to get build-script to run swift driver tests? We can avoid regressions from swift compiler to regress swift-driver test.

Let me ask around to see if what we need to do to unblock a new windows toolchain.

[compnerd]

@cachemeifyoucan build-script does not support Windows. If you mean if we can add it to build.ps1 ... we can try. The problem is that it will add a significant amount of time to the builds as it will require a secondary (tertiary) build of swift-driver and its dependencies.

[cachemeifyoucan]

Yeah, we don't test swift-driver again for macOS and Linux as well. Let me see if I can get docker updated and fix the issue first. We can discuss swift-driver testing later.